Railway points, also known as railway track switches, are a necessary part of all railway networks as they enable different routes through the network to be selected. They are a critical part of the network as a points failure often leads to delays, re-routing and cancellations. Even when fully operational, railway points represent a significant capacity constraint because they have to be operated in such a way to ensure that a route has been correctly set before rolling stock is allowed to pass the railway track junction.
In a traditional set of railway points, movable switch rails are located between stock rails. The stock rails are securely fixed to prevent movement and the free ends of the switch rails, which are linked together via stretcher bars, slide on suitable supports when commanded to move enabling either a straight route or a turnout route to be selected. Upon request from the signalling system, an actuator, which forms part of the lineside points operating equipment, moves the two switch rails via a linkage before locking the switch rails in position and communicating the detected position of the rails and the lock back to the signalling system. It is only once this process is complete that a train can be authorised to safely pass the track junction because during the ‘transition’ state, when the switch rails are not properly set to select either the straight route or the turnout route, the points present a derailment risk.
In an alternative type of railway points, commonly known as a stub switch, the ends of a pair of movable switch rails are moved between different positions into alignment with pairs of static stock rails to form a continuation of the main fixed rails on either side of the railway track junction. Stub switches have never achieved widespread usage for a number of reasons. One reason is difficulty aligning the free rail ends. If not correctly aligned, the loads on the free rail ends imparted by rolling stock can lead to premature wear of the rail ends and hence failure of the stub switch. Severe misalignment can, of course, also present a derailment risk. Another reason is that, as the rails expand during hot weather, the clearance between the free rail ends decreases and in extreme cases they can become jammed preventing movement of the switch rails and hence failure of the stub switch. Nevertheless, stub switches arguably offer significant advantages over the traditional railway points discussed above, including a reduced likelihood of blockages, the possibility of multiple routes from a single set of points, and cheaper modular construction using standard components.
A first object is, therefore, to provide a railway points arrangement, based on the stub switch design, which overcomes the drawbacks outlined above that are associated with railway points based on the traditional and stub switch designs.
Points operating apparatus (often referred to as lineside points operating equipment) is a key element of all railway points arrangements. Conventional points operating apparatus includes an actuator arrangement which moves the switch rails between different positions to select a desired route, for example a straight route or a turnout route, through a railway track junction. The actuator arrangement also locks the switch rails in the selected position.
In a traditional railway points arrangement, there is always a ‘transition’ state when the switch rails are not properly set to select either the straight route or the turnout route. When the switch rails are in this transition state, the points present a derailment risk, especially when rolling stock is executing a facing-point movement. If there is a failure of the points operating apparatus, for example a failure of part of the actuator arrangement, during this transition state, the switch rails of a conventional points arrangement become stuck in the transition state and cannot be moved by adjacent points operating apparatus because the faulty actuator arrangement prevents such movement. The points arrangement is consequently rendered inoperable and rolling stock cannot safely pass the railway track junction until remedial action is taken to repair or replace the points operating apparatus so that the points arrangement can be put back into service.
A second object is, therefore, to provide an improved railway points operating apparatus.
A conventional railway track junction 210 which allows rolling stock to follow different routes through the rail network is illustrated in FIG. 16. The railway track junction 210 includes a points arrangement 216, also known as a railway track switch, which enables different routes, for example a straight route 212 and a turnout route 214, to be selected through the railway track junction 210 by allowing rolling stock to transfer between different railway tracks. The points arrangement 216 illustrated in FIG. 1 comprises a traditional set of railway points in which movable switch rails 218 are located between stock rails 220. The stock rails 220 are securely fixed to prevent movement and the free ends of the switch rails 218, which are linked via stretcher bars (not shown in FIG. 1), slide transversely on suitable supports when commanded to move enabling either the straight route 212 or the turnout route 214 to be selected. As mentioned above, in an alternative type of railway points, commonly known as a stub switch, the ends of a pair of movable switch rails are moved transversely between different positions into alignment with pairs of fixed stock rails to form a continuation of the main fixed rails on either side of the railway track junction.
The railway track junction 210 includes a railway track crossing 222 where the rails of one track (e.g. the straight track) cross the rails of the other track (e.g. the turnout track). Also known as a “common crossing” or “frog”, the railway track crossing 222 includes a v-section nose 224 which is formed by a pair of fixed diverging rails 226 (one of each track). A pair of wing rails 228 is located on either side of the nose 224 to strengthen the structure (transmit longitudinal stress) and to provide a smooth transfer of load.
In a “fixed” crossing such as that shown in FIG. 16, which is the most common type of railway track crossing, the v-section nose 224 and wing rails 228 are fixed in position and the wing rails 228 are spaced apart from the v-section nose 224 by a small distance to form a groove 230 between each wing rail 228 and the nose 224 through which the wheel flanges of the rolling stock wheels can pass. Check rails 234 are provided to ensure that the wheels follow the correct route through the railway track crossing 222 and to ensure that the rolling stock does not derail. Before a wheel flange can engage in one of the grooves 230, the wheel must first traverse a gap 232 formed by the other groove 230 between the nose 224 and the other wing rail 228. The wheel is temporarily unsupported as it traverses this gap 232 and the impact between the wheel and the nose/wing rails results in both noise and an increased rate of wear of the nose 224 and the wing rails 228. In an attempt to address these problems, “swing nose” and “swing wing” crossings have been proposed.
In a swing nose crossing, the v-section nose 224 can move transversely so that it contacts one of the wing rails 228 and closes the gap 232 between the nose 224 and the wing rail 228 to provide a continuous length of rail for the wheels of the rolling stock. It will be appreciated that the position of the nose 224 (and hence which of the wing rails 228 it contacts) will vary according to the setting of the points arrangement 216 and, hence, whether the straight track or the turnout track needs to be selected. Swing nose crossings can either be “passive”, meaning that the v-section nose 224 is moved transversely by the wheels of rolling stock, or “active”, meaning that the v-section nose 224 is moved by an actuator arrangement. It should be noted that in a “passive” swing nose crossing, the v-section nose 224 is only moved transversely by the wheels of rolling stock when the rolling stock passes through the crossing in the trailing-point direction, i.e. the converging direction of the rails forming the v-section nose 224.
In a swing wing crossing, the v-section nose 224 is fixed and one or both of the wing rails 228 is movable. One example of a “passive” swing wing crossing is described in GB 1587042. In this passive arrangement, one of the wing rails is fixed whilst the other wing rail is flexible and can be moved transversely, from a closed position to an open position, by a passing wheel of rolling stock. In the closed position (set for the straight route), the flexible wing rail contacts the nose to provide a continuous running surface along the straight route for the rolling stock wheels. In the open position (set for the turnout route), the movable wing rail is pushed away from the nose by a passing wheel flange so that the rolling stock can travel along the turnout route. When following the turnout route, the wheels still have to traverse a gap between the fixed wing rail and the nose but this is not problematic if the turnout speed is quite low. In practice, there is an increasing demand for higher turnout speeds in order to increase network capacity. As a result, “active” swing wing crossings have been proposed in which an actuator arrangement is provided to move the wing rails transversely into and out of contact with the nose so that there are no gaps (i.e. a continuous running surface) when rolling stock travels along either the straight route or the turnout route.
Despite the obvious advantages of swing nose and swing wing crossings, including reduced wear of the v-section nose and wing rails, reduced noise and higher possible turnout speeds, they have seen limited use in the UK. This is because the aforementioned advantages are outweighed by disadvantages such as high cost, complexity and poor reliability. In fact, swing nose crossings are no longer fitted on the UK mainline rail network due to performance and reliability issues.
A third object is, therefore, to provide a railway track crossing which overcomes these disadvantages.